Messages in this thread | | | From | Daeho Jeong <> | Date | Mon, 8 Jun 2020 16:19:43 +0900 | Subject | Re: [f2fs-dev] [PATCH] f2fs: add F2FS_IOC_TRIM_FILE ioctl |
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Yes, I agree with you about each vendor has different implementation on discard. So, we might be gonna use the combination of zeroing and send discards for a more secure solution. :) I think we still need a discard interface to unmap from the mapping table of the storage device side.
Thanks,
2020년 6월 8일 (월) 오후 3:57, Chao Yu <yuchao0@huawei.com>님이 작성: > > On 2020/6/8 11:36, Daeho Jeong wrote: > > Yes, this is for security key destruction. > > > > AFAIK, discard will unmap the data block and, after done it, > > we can read either zero data or garbage data from that block depending > > on eMMC/UFS. > > Since spec didn't restrict how vendor implement the erase interface, so > in order to enhance performance of discard interface, vendor could implement > it as an async one, which may not zero mapping entry(L1 table), instead, it > could set related bitmap to invalid that mapping entry, than later if device > allow user to access that invalid mapping entry, key info may be explosed, > > It's completely up to how vendor implement the interface, so I think there is > still risk to use discard. > > Thanks, > > > In a view point of read data, it might be the same with zeroing the data block. > > However, since we can even unmap that block, I believe discard is > > safer than zeroing out. > > > > 2020년 6월 8일 (월) 오전 11:46, Chao Yu <yuchao0@huawei.com>님이 작성: > >> > >> On 2020/6/5 12:27, Daeho Jeong wrote: > >>> From: Daeho Jeong <daehojeong@google.com> > >>> > >>> Added a new ioctl to send discard commands to whole data area of > >>> a regular file for security reason. > >> > >> I guess this interface is introduced for security key destruction, if I'm > >> right, however, IIRC, discard(erase) semantics in eMMC/UFS spec won't > >> guarantee that data which was discard could be zeroed out, so after discard, > >> the key still have risk of exposure. So instead, should we use sb_issue_zeroout()? > >> > >> Thanks, > >> > >>> > >>> Signed-off-by: Daeho Jeong <daehojeong@google.com> > >>> --- > >>> fs/f2fs/f2fs.h | 1 + > >>> fs/f2fs/file.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++ > >>> 2 files changed, 130 insertions(+) > >>> > >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > >>> index c812fb8e2d9c..9ae81d0fefa0 100644 > >>> --- a/fs/f2fs/f2fs.h > >>> +++ b/fs/f2fs/f2fs.h > >>> @@ -434,6 +434,7 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal, > >>> _IOR(F2FS_IOCTL_MAGIC, 18, __u64) > >>> #define F2FS_IOC_RESERVE_COMPRESS_BLOCKS \ > >>> _IOR(F2FS_IOCTL_MAGIC, 19, __u64) > >>> +#define F2FS_IOC_TRIM_FILE _IO(F2FS_IOCTL_MAGIC, 20) > >>> > >>> #define F2FS_IOC_GET_VOLUME_NAME FS_IOC_GETFSLABEL > >>> #define F2FS_IOC_SET_VOLUME_NAME FS_IOC_SETFSLABEL > >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >>> index dfa1ac2d751a..58507bb5649c 100644 > >>> --- a/fs/f2fs/file.c > >>> +++ b/fs/f2fs/file.c > >>> @@ -3749,6 +3749,132 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg) > >>> return ret; > >>> } > >>> > >>> +static int f2fs_trim_file(struct file *filp) > >>> +{ > >>> + struct inode *inode = file_inode(filp); > >>> + struct f2fs_sb_info *sbi = F2FS_I_SB(inode); > >>> + struct address_space *mapping = inode->i_mapping; > >>> + struct bio *bio = NULL; > >>> + struct block_device *prev_bdev = NULL; > >>> + loff_t file_size; > >>> + pgoff_t index, pg_start = 0, pg_end; > >>> + block_t prev_block = 0, len = 0; > >>> + int ret = 0; > >>> + > >>> + if (!f2fs_hw_support_discard(sbi)) > >>> + return -EOPNOTSUPP; > >>> + > >>> + if (!S_ISREG(inode->i_mode) || f2fs_is_atomic_file(inode) || > >>> + f2fs_compressed_file(inode)) > >>> + return -EINVAL; > >>> + > >>> + if (f2fs_readonly(sbi->sb)) > >>> + return -EROFS; > >>> + > >>> + ret = mnt_want_write_file(filp); > >>> + if (ret) > >>> + return ret; > >>> + > >>> + inode_lock(inode); > >>> + > >>> + file_size = i_size_read(inode); > >>> + if (!file_size) > >>> + goto err; > >>> + pg_end = (pgoff_t)round_up(file_size, PAGE_SIZE) >> PAGE_SHIFT; > >>> + > >>> + ret = f2fs_convert_inline_inode(inode); > >>> + if (ret) > >>> + goto err; > >>> + > >>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>> + down_write(&F2FS_I(inode)->i_mmap_sem); > >>> + > >>> + ret = filemap_write_and_wait(mapping); > >>> + if (ret) > >>> + goto out; > >>> + > >>> + truncate_inode_pages(mapping, 0); > >>> + > >>> + for (index = pg_start; index < pg_end;) { > >>> + struct dnode_of_data dn; > >>> + unsigned int end_offset; > >>> + > >>> + set_new_dnode(&dn, inode, NULL, NULL, 0); > >>> + ret = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE); > >>> + if (ret) > >>> + goto out; > >>> + > >>> + end_offset = ADDRS_PER_PAGE(dn.node_page, inode); > >>> + if (pg_end < end_offset + index) > >>> + end_offset = pg_end - index; > >>> + > >>> + for (; dn.ofs_in_node < end_offset; > >>> + dn.ofs_in_node++, index++) { > >>> + struct block_device *cur_bdev; > >>> + block_t blkaddr = f2fs_data_blkaddr(&dn); > >>> + > >>> + if (__is_valid_data_blkaddr(blkaddr)) { > >>> + if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), > >>> + blkaddr, DATA_GENERIC_ENHANCE)) { > >>> + ret = -EFSCORRUPTED; > >>> + goto out; > >>> + } > >>> + } else > >>> + continue; > >>> + > >>> + cur_bdev = f2fs_target_device(sbi, blkaddr, NULL); > >>> + if (f2fs_is_multi_device(sbi)) { > >>> + int i = f2fs_target_device_index(sbi, blkaddr); > >>> + > >>> + blkaddr -= FDEV(i).start_blk; > >>> + } > >>> + > >>> + if (len) { > >>> + if (prev_bdev == cur_bdev && > >>> + blkaddr == prev_block + len) { > >>> + len++; > >>> + } else { > >>> + ret = __blkdev_issue_discard(prev_bdev, > >>> + SECTOR_FROM_BLOCK(prev_block), > >>> + SECTOR_FROM_BLOCK(len), > >>> + GFP_NOFS, 0, &bio); > >>> + if (ret) > >>> + goto out; > >>> +> + len = 0; > >>> + } > >>> + } > >>> + > >>> + if (!len) { > >>> + prev_bdev = cur_bdev; > >>> + prev_block = blkaddr; > >>> + len = 1; > >>> + } > >>> + } > >>> + > >>> + f2fs_put_dnode(&dn); > >>> + } > >>> + > >>> + if (len) > >>> + ret = __blkdev_issue_discard(prev_bdev, > >>> + SECTOR_FROM_BLOCK(prev_block), > >>> + SECTOR_FROM_BLOCK(len), > >>> + GFP_NOFS, 0, &bio); > >>> +out: > >>> + if (bio) { > >>> + ret = submit_bio_wait(bio); > >>> + bio_put(bio); > >>> + } > >>> + > >>> + up_write(&F2FS_I(inode)->i_mmap_sem); > >>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>> +err: > >>> + inode_unlock(inode); > >>> + mnt_drop_write_file(filp); > >>> + > >>> + return ret; > >>> +} > >>> + > >>> long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > >>> { > >>> if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(filp))))) > >>> @@ -3835,6 +3961,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > >>> return f2fs_release_compress_blocks(filp, arg); > >>> case F2FS_IOC_RESERVE_COMPRESS_BLOCKS: > >>> return f2fs_reserve_compress_blocks(filp, arg); > >>> + case F2FS_IOC_TRIM_FILE: > >>> + return f2fs_trim_file(filp); > >>> default: > >>> return -ENOTTY; > >>> } > >>> @@ -4004,6 +4132,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) > >>> case F2FS_IOC_GET_COMPRESS_BLOCKS: > >>> case F2FS_IOC_RELEASE_COMPRESS_BLOCKS: > >>> case F2FS_IOC_RESERVE_COMPRESS_BLOCKS: > >>> + case F2FS_IOC_TRIM_FILE: > >>> break; > >>> default: > >>> return -ENOIOCTLCMD; > >>> > > . > >
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